The seas inside the reef are generally calm, but that can't always be said of the dive sites outside the reef, of which there are many. It is really the luck of the weather card draw. I was a bit nervous the first time out, but all you have to do is ride the waves with your inflated BC and you are just fine. Sometimes, there's a bit of whacking about trying to get back onto the boat, but if you are in fairly good shape, it shouldn't be anything you can't handle. You and I are about on par from what you tell us.
I go down by myself quite often and have never had too much trouble meeting people. The only times it has ever been difficult was if I was feeling insecure within myself. If you just talk to people, they will gladly talk to you and if they aren't friendly, to hell with them, and move on to someone nicer. Most everyone on vacation came to have a good time and they are pleased to make new acquaintances. Go diving, go on some tours, have some drinks at Fido's bar and you'll be on your way.
Watch out for those friendly sharks up on shore though!! (wicked grin)
A fish and a bird can fall in love, but where will they build their nest?